Electrical connector

ABSTRACT

An electrical connector for crimping onto wires including a ferrule-forming portion having its inner surface formed with a plurality of grooves with generally flat land surfaces therebetween, at least some of said grooves having an undercut side surface, preferably of at least about 1* to 6* for the purpose of shearing portions of wire crimped therein to expose the bare metal underlying any layer of insulation, corrosion, etc. thereon in order to provide the necessary low ohmic electrical path between wire and connector as well as a superior mechanical connection therebetween.

ilite tates t UDonnoll et al.

ELECTCAL CUNNECTUR Inventors: Paul E. ODonneill, Whitman; ll-l. VincentMarshfield, both of Mass.

Assignee: Ark-Les Switch Corporation, Watertown, Mass. Filed: Apr. 19,1972 Appl. No.: 245,523

U.S. (Ii 339/97 C, 339/276 T lint. Cl. ..ll-I01r 9/08 Field of Search..339/95, 97-99,

[56] Relierences Cited UNITED STATES PATENTS 2/1962 Berg ..339/276 T3,111,554

11/1963 Harris ..339/276 R May 22, R973 Primary Examiner-Joseph H.McGlynn Att0rney-Martin Kirkpatrick [57] ABSTCT An electrical connectorfor crimping onto wires including a ferrule-forming portion having itsinner surface formed with a plurality of grooves with generally flatland surfaces therebetween, at least some of said grooves having anundercut side surface, preferably of at least about 1 to 6 for thepurpose of shearing portions of wire crimped therein to expose the baremetal underlying any layer of insulation, corrosion, etc. thereon inorder to provide the necessary low ohmic electrical path between wireand connector as well as a superior mechanical connection therebetween.

10 Claims, 7 Drawing Figures ELECTRICAL CONNECTOR This invention relatesto electrical connectors of the type which are adapted to be crimpedonto wires, and more particularly to such connectors which areespecially suitable for crimping onto wires having a thin insulatingcoating thereon.

Many types of wires used in making electrical connections have thininsulating coatings thereon, either applied thereto as with so-calledmagnet wire, or naturally occurring as with aluminum wire which developsan oxide coating. When it is desired to make electrical connection towires having such coatings it is necessary during the mechanicalcrimping operation to pierce the insulating coating in order to achievea connection of suitable mechanical strength and an electrical contactof low ohmic resistance with the current carrying portion of the wire.

Although attempts have been made to achieve the desired results, theyhave been deficient in some respects, especially as to the necessay lowohmic contact resistance when certain types of insulating coatings arepresent on the wire.

Accordingly, it is a major object of the present invention to provide anelectrical connector to be crimped onto one or more wires having aninsulating coating by mechanical methods and which thereby creates aconnection of suitable mechanical strength and an electrical contact oflow ohmic resistance with the current carrying portion of the wire.

The above and further objects of the invention are accomplished byproviding an electrical connector including a ferrule-forming portionhaving its inner surface formed with a plurality of novel grooves withgenerally flat land surfaces therebetween, at least some of said grooveshaving a sharp edged undercut side surface for shearing the wire as itis forced into the undercut. If desired an upset burr may be provided atthe sharp edge. Preferably there are at least two grooves parallel toand spaced from one another by the land surface, the grooves havingtheir side surfaces remote from the groove undercut by about 1 to 6. Theside surfaces of the grooves contiguous with the central land are slopedat an obtuse angle of more than 90 Further grooves have their sidesurfaces most remote from the central land undercut.

For the purpose of more fully explaining the above and still furtherobjects and features of the invention, reference is now made to thefollowing detailed description of a preferred embodiment of theinvention, together with the accompanying drawings, wherein:

FIG. l is a plan view of the connector of the invention in flat form;

FIG. 2 is an enlarged cross-sectional view of the connector of FIG. 1,taken along the line 2--2 thereof;

FIG. 3 is an end view of the connector of FIG. 1 bent into ferrule formfor receiving wires therein;

FIG. 4 is a plan view, partly in section, of the connector of FIG. 11crimped onto two solid wires;

FIG. 5 is a cross-sectional view of the crimped connector and wires ofFIG. 4, taken along the line 5-5 thereof;

FIG. 6 is an enlarged cross-sectional view of a portion of the crimpedconnector of FIG. 4, showing the sheared wire portion within theundercut; and

FIG. 7 is an enlarged view of a modification of the connector of FIGS. 1through 6 showing an upset burr.

Referring to FIGS. 1 through 6, the connector of the preferredembodiment of the invention is of sheet metal such as brass, having agrooved inner surface and a flat outer surface 15 with a conventionalring tongue portion 12 and a ferrule-forming portion, generallydesignated 14, into which wires l6, 13 having a thin insulating coating17 (FIG. 6) may be crimped.

According to the invention, the ferrule-forming portion 14 has its innersurface formed with a plurality of parallel grooves with generally flatland surfaces therebetween, with at least some of said grooves having anundercut side surface, preferably of at least about 1 to 6, for thepurpose of shearing portions of wire crimped therein to expose the baremetal underlying any layer of insulation, corrosion, etc. thereon inorder to provide the necessary low ohmic electrical path between wireand connector as well as a superior mechanical connection therebetween.

More specifically, as best shown in FIGS. 1 and 2 in its flat form,ferrule portion 14 as illustrated has six parallel grooves separated byfive flat surfaced lands, including a central land 20. Grooves 22, 32 onopposite sides of central land 20 are mirror images of one another andhave their opposite generally straight side surfaces 23, 33 remote fromcentral land 20 undercut, in accordance with the present invention, atan angle, U, with respect to the perpendicular to the surfaces offerrule-forming portion 14, of at least 1 to 6, as shown. A greaterundercut angle, U, may also be employed. The undercut side surfaces 23,33 form an edge contiguous with their respective lands 24, 34 which isrelatively sharp for effective shearing of the wire and its insulatingcoating 17, and may, if desired, include thereon a projection in theform of a burr 40, as shown in FIG. 7, to aid in piercing the wire andits insulating coating 17 (FIG. 6).

The generally straight side surfaces 25, 35 contiguous with central land20 are sloped at an obtuse included angle of more than 90 degrees withrespect to the inner surface of ferrule-forming portion 20, preferablyabout 140 as shown, plus or minus 20. Generally flat bottom groovesurfaces 27, 37 extend between side surfaces 23, 25 and 33, 35respectively, although a bottom surface other than flat may be used ifdesired. The width of grooves 22, 32 is relatively narrow, preferablyabout 0.01 to 0.02 inches.

Additional grooves with intervening flat lands are preferably providedon ferrule-forming portion 14, with their side surfaces most remote fromcentral land surface 20 undercut as set forth above. Thus grooves 26 and28, identical in configuration with groove 22, with a flat land 29therebetween, are provided outwardly of land 24 away from central land20 and grooves 36 and 38, identical in configuration with groove 32,with a fiat land 39 therebetween are provided outwardly of land 24 awayfrom central land 20.

For use, the ferrule-forming portion 14 of the connector of theinvention is normally first bent into U shape, as shown in FIG. 3, forreceiving the wires, whether solid or stranded, to be crimped thereby.Thereafter, a crimping operation is carried out by conventionalapparatus wherein the ferrule-forming portion 14 is forced inwardlyagainst the wires 16, 18 under sufficiently heavy pressure to deform thewire by shearing it and driving it into the grooves, as shown in FIGS. 4and 5 and particularly in the enlarged view of FIG. 6 wherein isillustrated the shearing of the insulating coating 17 as the metal ofthe wire is forced into the grooves and under their undercut sidesurfaces. This action, unique to the undercut grooves of the presentinvention, not only provides the necessary low ohmic path between wireand connector, but also provides a superior mechanical connectiontherebetween in both directions along the axis of the crimped connectorby reason of the positioning of undercut side surfaces on opposite sidesof the grooves with respect to the central land 20, so that stress ineither direction is equally well resisted.

What is claimed is: 1. An electrical connector for crimping onto wiresincluding a ferrule-forming portion having its inner surface formed witha plurality of grooves with generally flat land surfaces therebetween atleast some of said grooves having an undercut side surface. 2. Anelectrical connector as claimed in claim 1 wherein said undercut sidesurface is generally straight. 3. An electrical connector as claimed inclaim 2 wherein said side surface is undercut at an angle of about 1 to6.

4. An electrical connector for crimping onto wires including aferrule-forming portion having its inner surface formed with a pluralityof at least two grooves with a land surface therebetween said twogrooves being parallel to and spaced from one another by said landsurface with their opposite side surfaces remote from said land beingundercut. 5. An electrical connector as claimed in claim 4 wherein theside surfaces of said grooves contiguous with said land are sloped at anobtuse angle of more than 6. An electrical connector as claimed in claim5 wherein said undercut is at an angle of about 5.

7. An electrical connector for crimping onto wires including aferrule-forming portion having its inner surface formed with a pluralityof at least four parallel grooves with flat land surfaces therebetweenthe central two of said grooves being parallel to and spaced from oneanother by the central one of said land surfaces with their oppositeside surfaces remote from said central land surfaces being undercut theother of said grooves having their side surfaces most remote from saidcentral land surface being undercut. 8. An electrical connector asclaimed in claim 7 wherein the side surfaces of said grooves contiguouswith said central land and of said other grooves closest to said centralland is sloped at an obtuse angle of more than 90. 9. An electricalconnector as claimed in claim 8 wherein said undercut has a sharp edgeat its contiguous land and is at an angle of about 5 and said obtuseangle is of about l60. 10. An electrical connector as claimed in claim 9wherein the bottom of said grooves is generally flat and of a width fromabout 0.01 to 0.02 inches.

2. An electrical connector as claimed in claim 1 wherein said undercutside surface is generally straight.
 3. An electrical connector asclaimed in claim 2 wherein said side surface is undercut at an angle ofabout 1* to 6*.
 4. An electrical connector for crimping onto wiresincluding a ferrule-forming portion having its inner surface formed witha plurality of at least two grooves with a land surface therebetweensaid two grooves being parallel to and spaced from one another by saidland surface with their opposite side surfaces remote from said landbeing undercut.
 5. An electrical connector as claimed in claim 4 whereinthe side surfaces of said grooves contiguous with said land are slopedat an obtuse angle of more than 90*.
 6. An electrical connector asclaimed in claim 5 wherein said undercut is at an angle of about 5*. 7.An electrical connector for crimping onto wires including aferrule-forming portion having its inner surface formed with a pluralityof at least four parallel grooves with flat land surfaces therebetweenthe central two of said grooves being parallel to and spaced from oneanother by the central one of said land surfaces with their oppositeside surfaces remote from said central land surfaces being undercut theother of said grooves having their side surfaces most remote from saidcentral land surface being undercut.
 8. An electrical connector asclaimed in claim 7 wherein the side surfaces of said grooves contiguouswith said central land and of said other grooves closest to said centralland is sloped at an obtuse angle of more than 90*.
 9. An electricalconnector as claimed in claim 8 wherein said undercut has a sharp edgeat its contiguous land and is at an angle of about 5* and said obtuseangle is of about 120* -160*.
 10. An electrical connector as claimed inclaim 9 wherein the bottom of said grooves is generally flat and of awidth from about 0.01 to 0.02 inches.